Abstract: Salt cavern compressed air energy storage (CAES) is currently an important technique for grid peak regulation using renewable energy sources such as wind and solar power. However, daily gas injection and withdrawal result in high-frequency and high-amplitude fluctuations in the wet environment within the salt cavern. When the cavern temperature drops during gas withdrawal, the relative humidity can reach nearly 100%, causing the surrounding rock salt to deliquesce, which leads to lateral expansion of the cavern and affects its stability and tightness. This study involved exposing damaged rock salt to dry-wet cycles that mimic CAES operation conditions, and measuring the amount of deliquescence. The variation of the deliquescent rate on the salt surface with the deviation stress level was analyzed using the visual morphology, and their fitting relationship was established. A cell apoptosis method for FLAC^3D was developed, which was embedded in the numerical program simulating the long-term deformation of salt caverns. The subroutine calculates the deliquescent amount of the surrounding rock salt cells and induces their apoptosis at appropriate time, to characterize the macroscopic effect of deliquescence on the usability of salt caverns. The results show that after long-term operation, the cavern slightly extends outward due to the deliquescence of the surrounding rock, causing a slight deterioration in the displacements and the safety factor of the cavern wall, but still adequately satisfying the empirical safety criterion. However, deliquescent salt traps moisture in the air, which accumulates at the cavern bottom as brine, significantly reducing the cavern’s available volume. This change is more significant than creep shrinkage and requires control through the use of ground dehumidifiers and regular brine discharging.

Key words: salt cavern compressed air energy storage (CAES), rock salt, dry-wet cycle, deliquescence, secondary development